Body composition

Question 1

What is body composition?

Answer 1

=The body’s relative amounts of fat and lean body tissue (fat free mass)

Question 2

What are the components of fat free mass?

Answer 2

-Muscle
-Bone
-Water
-Organ tissues

Question 3

Formula to calc total body fat?

Answer 3

Essential fat + storage fat

Question 4

What is the purpose of essential fat and where is it located

Answer 4

-required for normal physiological function
-Is fat within major organs, muscle and CNS

Question 5

Difference in essential fat between male and females

Answer 5

-Women have more essential fat (12%) compared to males (3%)

Question 6

What is storage fat?

Answer 6

-Nonessential fat stored as adipose tissue near the body’s surface

Question 7

What is % body fat?

Answer 7

-% of total body weight that is fat
-is primary way to evaluate body composition

Question 8

How to calc fat free mass?

Answer 8

Body mass- fat mass

Question 9

Why is body composition measured?

Answer 9

-to help assess health risks and determine needed behaviour changes for optimal health
-to help athletes determine the best body composition for performance in their sport

Question 10

Effects of too little body fat?

Answer 10

-reproductive disorders
-circulatory disorders
-immune disorders

Question 11

Effects of too much body fat?

Answer 11

-cardiovascular disease
-hypertension
-type 2 diabetes
-cancer

Question 12

What is a 2 compartmental model of body comp

Answer 12

-splits body into fat free mass and fat mass and suggests one of these components is determined and the other is estimated from the result

Question 13

What is a 3 compartmental model of body comp

Answer 13

Includes bone mineral content in addition to fat free and fat mass

Question 14

What is a 4 compartmental model of body comp

Answer 14

Also includes total body water

Question 15

What are the different methods used to assess body composition?

Answer 15

-height; weight and BMI
-waist to hip ratio
-hydrostatic weighing
-skin fold measurements
-air displacement plethysmography
- dual x ray absorptiometry (DEXA)
-bio electrical impedance analysis (BIA)

Question 16

How to measure height?

Answer 16

-use stadiometer
-ensure participant removes shoes, stands up straight with heels together and holds deep breath during measurement

Question 17

How to measure weight?

Answer 17

-measure on calibrated scale
-ensure subject removes shoes and wears minimal clothing (nude if possible)

Question 18

BMI formula/ healthy ranges

Answer 18

=weight (kg) / height (m2)
-underweight <18.5
-normal 18.5- 24.9
-overweight 25-29.9
-obese 30-34.9
Extremely obese 35<

Question 19

How to measure wait to hip ratio

Answer 19

-waist circumference- measured at narrowest point below ribs
-hip circumference- measured at widest point

Question 20

How to measure using skin fold tests

Answer 20

-multiple sights are measured and % BF is calculated using some of sites
-measurements should be taken on right side of body

Question 21

What is used when performing skin folds and in what 2 ways can they be used?

Answer 21

-used callipers to measure thickness of double layer of skin
-used to track changes in individuals or sum of the skin folds or sum of multiple skin fold sites can be used with equation to calc % body fat

Question 22

Limitations of skin fold tests

Answer 22

-possible technician error
-skinfold thickbess can be affected by factors other than amount of fat: excercise increases skin thickness, dehydration reduces it, dermatitis increases it

Question 23

What are the 2 2 compartmental models?

Answer 23

-air displacement plethysmography
-BIA

Question 24

How does air displacement plethysmography work

Answer 24

-calculated %BF from body density and uses computerised air pressure sensors to determine amount of air displaced while participant is in bod pod

Question 25

How does BIA work

Answer 25

-rapid, non invasive and inexpensive
-sends electrical current thru body to estimate body fat (based on idea that fat is less conductive than lean tissue)

Question 26

Describe how DEXA works

Answer 26

• is a 3 compartmental model
  -used a series of low dose radiation scans providing high accuracy
  -provided measurements of bone mineral, fat and non bone lean tissue

Question 27

Hydro-densitometry method?

Answer 27

-2 compartmental and indirect

Question 28

Hydro-densitometry method pros and cons

Answer 28

+can be accurate when carried out by qualified person
-assumption of specific tissue densities (differ in
elite athletic populations)
- residual lung volume can be a source of error
- Claustrophobia/fear whilst underwater
- Expensive equipment. Needs maintenance,
sterilisation and cleaning
- cannot measure distribution of FFM or FM
- air can be contained within an individual’s
swimsuit, skin, head, body hair, digestive
tract…leads to false estimations
- air temperature, barometric pressure, nitrogen
analyser and force sensor calibrations all can lead
to measurement error
- is time consuming and needs expertise.

Question 29

Air displacement plethysmography pros and cons?

Answer 29

+Overcomes several of the aforementioned
limitations of hydro-densitometry
+ Reliable
- Not sensitive enough for changes in elite
athletic body composition
-Too sensitive to clothing, body hair, air
movement, moisture, pressure and
temperature changes
-expensive to buy equipment.
-Overestimates BF% compared with hydro-
densitometry
- Body fat measures diverge at the extremes of
the BMI spectrum (concern in certain athletic
populations)
- cannot measure distribution of FFM or FM

Question 30

BIAS pros and cons?

Answer 30

+ Speed
+ minimal expertise required
+ portability
+ cost (compared to other methods)
-Can be affected by temperature and hydration
status
-sensitivity to conductive surface of electrodes and
electrode placement
- Assumptions on the composition of the body in
formula and calculations, irrespective of population group
-the limbs contribute a large proportion to whole-
body impedance, despite the relatively low
contribution to overall BM [31].
- Limited validation in athletic populations
-Some under and overestimation of FFM
-There is also large variability between devices

Question 31

Ultrasound pros and cons

Answer 31

-is multi compartmental
+ Reliable and accurate measure of subcutaneous
adipose tissue thickness
+ MAY be portable*
- Affected by the chosen frequency, pressure
and orientation of the probe causing
measurement error
-Requires technician expertise
-Can be expensive and impractical within the
applied setting, even with improved
portability

Question 32

DEXA pros and cons

Answer 32

-is multi compartmental
+ Reliable measure of body composition
+Measures Bone Mineral Content (low energy
availability etc)
+ Limb-specific estimations of FM and FFM which
can be useful when tracking injured athletes
-Uses radiation: legal and ethical constraints
(approval by doctor /national ethics committee)
- Requires trained and certified technician
- Variations between manufacturers (energy levels
emitted, pixel size, software algorithms etc)
-Expensive equipment
-Not portable
-Time consuming
-Not reliable at extremes of size (very large people)
- Affected by water and glycogen levels